------- Comment #4 from grosser at gcc dot gnu dot org 2008-09-18 16:25 ------- Created an attachment (id=16355) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16355&action=view) Create single entry single exit edges for the SCoPs of the SCoP detection
Here is a idea how to handle the single exit single entry edges. Have also a look at this mail: http://gcc.gnu.org/ml/gcc-patches/2008-09/msg01324.html I would just like to discuss the idea. A little explanation that was not possible during our phone call today (Since about two minutes my internet is working again) During SCoP detection we can not represent the SCoPs as a single exit single entry region as it is described in the graphite.h SCOP_REGION, as this data structure uses a single edge to describe e.g. the entry. But code like | 1 2 | | / | |/ | 3 <- entry | |\ | | | | 4 ^ | | | | |/ | 5 is also single entry, even if we do not have a single entry edge. But the edges (1->3, 2->3) can easily be combined using a forwarder bb. | 1 2 | | / | |/ |3.0 | | (3.0 -> 3.1) = entry edge |3.1 <- entry | |\ | | | | 4 ^ | | | | |/ | 5 */ Here we get a single entry edge. If we do not want to modify the CFG during SCoP detection, we have to use a representation (sd_region), that is able to represent SCoPs like the above. After SCoP detection we can introduce forwarder blocks, to be able to use a single edges to describe the entry and exit points. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37372